Valachi, a low-ranking member of the New York-based Genovese crime family, was the first ever government witness coming from the American Mafia itself. Before Valachi, federal authorities had no concrete evidence that the American Mafia even existed. His disclosures never led directly to the prosecution of many Mafia leaders, but he was able to provide many details of its history, operations and rituals, aiding in the solution of several uncleared murders, as well as naming many members and the major crime families.

Valachi testified in vivid and minute detail on his day-to-day life in organized crime in a first-time-ever public account of life as a soldier of La Cosa Nostra, including its rites of initiation.[4] These televised hearings brought home to average Americans the savage violence and intimidation routinely used by the Mafia to further and protect its criminal enterprises.[5]

Valachi disclosed that the Mafia was called Cosa Nostra ("our thing" or "this thing of ours") among the members of the organisation.[1][2][6] At the time, it was understood as a proper name, fostered by the FBI and disseminated by the media. The designation gained wide popularity and almost replaced the term Mafia. The FBI even added the article La to the term, calling it La Cosa Nostra (in Italy, the article la precedes the general "mafia" term but is not used before "Cosa Nostra").

He also revealed the organisational structure of the Mafia with "soldiers" organized into "regimes" and led by a "caporegime" ("lieutenant"). The regimes, in turn, are organized into "families" and bossed by "capos" (bosses), each representing a geographic area, who make up Cosa Nostra's Commission, the final arbiter of the syndicate's affairs.[6][7]

The assassination of President Kennedy one month after the hearings took a lot of steam out of RFK's war on the Mafia. However, later, due in part to Valachi's disclosures, the United States Congress eventually passed two new laws to strengthen federal racketeering and gambling statutes to aid the Federal Bureau of Investigation's fight against mob influence. The Omnibus Crime Control and Safe Streets Act of 1968 provided for the use of court-ordered electronic surveillance in the investigation of certain specified violations.

The Racketeer Influenced and Corrupt Organizations (RICO) Statute of 1970 allowed organized groups to be prosecuted for all of their diverse criminal activities, without the crimes being linked by a perpetrator or all-encompassing conspiracy. Along with greater use of Agents for undercover work by the late 1970s, these provisions helped the FBI develop cases that, in the 1980s, put almost all the major traditional crime family heads in prison.[9]

In 1964 the US Department of Justice urged Valachi to write down his personal history of his underworld career. Although Valachi was only expected to fill in the gaps in his formal questioning, the resulting account of his thirty-year criminal career was a rambling 1,180-page manuscript titled The Real Thing.[3][10][11]

Attorney General Nicholas Katzenbach authorized the public release of Valachi’s manuscript. He hoped that publication of Valachi’s story would aid law enforcement and possibly encourage other criminal informers to step forward. Author Peter Maas, who broke Valachi’s story in The Saturday Evening Post, was assigned the job of editing the manuscript and permitted to interview Valachi in his Washington, D.C., jail cell.[10][11]

The American Italian Anti-Defamation League promoted a national campaign against the book on the grounds that it would reinforce negative ethnic stereotypes. If the book’s publication was not stopped they would appeal directly to the White House. Katzenbach reversed his decision to publish the book after a meeting with President Lyndon B. Johnson; an action that embarrassed the Justice Department.[10][11]

In May 1966, Katzenbach asked a district court to stop Maas from publishing the book—the first time that a U.S. attorney general had ever tried to ban a book. Maas was never permitted to publish his edition of Valachi’s original memoirs, but he was allowed to publish a third-person account based upon interviews he himself had conducted with Valachi. These formed the basis of the book The Valachi Papers, which was published in 1968.[10][11] The book was made into the 1972 film The Valachi Papers starring Charles Bronson as Valachi.

Charles Brandt, I Heard You Paint Houses: Frank "the Irishman" Sheeran and the inside story of the Mafia, the Teamsters, and the last ride of Jimmy Hoffa, Steerforth Press, Hanover (NH, USA) 2004 (ISBN1-58642-077-1).